OpenAI made GPT-5.5 and GPT-5.5 Pro available to API developers on May 1, 2026. The standard GPT-5.5 is priced at $5 per million input tokens and $30 per million output tokens, with a 1M-token context window. GPT-5.5 Pro targets higher-accuracy workloads at $30 per million input tokens and $180 per million output tokens. The dual-tier release gives backend teams a cost-performance tradeoff on the same generation of model. The large context window enables longer document processing and multi-turn workflows without chunking. Teams already on OpenAI's API can access both models without additional onboarding, though the Pro tier's pricing is aimed at production workloads where accuracy gains justify the cost.